Are Australia’s coal and gas generators fit for purpose to power Australia through next summer’s heatwaves? The evidence of last summer suggests they cannot be relied upon, with a new report showing how coal plants melted in the heat in Queensland on a day of record demand.

The Australian Energy Regulator has documented yet another occasion when fossil fuel generators failed to perform in the midst of a heatwave, raising questions about the ability of the country’s ageing coal fleet to meet demand in future heatwaves.

A new report from the AER looks at the soaring electricity prices on February 12, 2017, when high temperatures across the state caused record demand despite the day being a Sunday, when most business and much manufacturing was closed.

The principal reason, the AER notes, was the sudden withdrawal of more than 790MW of coal and gas capacity – all due to technical faults related to the heat.

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The plants’ absence nearly created a shortfall of supply, with emergency back-up called on as the 5-minute price soared to more than $13,000/MWh on 11 occasions between 4.35pm and 7.05pm, to meet surging demand that tipped at a record 9,369MW.

The AER report on the events of February 12 is the latest of a string of reports noting how coal and gas plants have failed, or lost capacity due to problems in the heat.

Just a few days earlier, on February 10 in NSW, the loss of 1,000MW of coal capacity and the sudden failure of another 1,200MW of gas generation nearly tipped the state into widespread blackouts.

Just four days before that, on February 6, a total of 3,000MW of coal and gas capacity was lost in NSW and Queensland, mostly due to heat related faults. And on March 3, the sudden failure of the two major gas generators almost caused another system black in South Australia.

On these occasions, authorities said that renewable energy was to thank for keeping the lights on. Other analysis has pointed out that rooftop solar has saved significant amounts in wholesale electricity costs, with one report putting the savings in NSW during the heatwave at nearly $1 billion.